Field of the Invention
The present invention relates to a semiconductor device and a semiconductor module, and particularly relates to a resin-sealed semiconductor device.
Description of the Background Art
As packages for semiconductor chips, there are known no-leads packages such as QFN (quad flat no-leads) and SON (small outline no-leads). In a general no-leads package, a semiconductor chip is bonded by a die bond resin onto a die pad of a lead frame. A terminal of the semiconductor chip is connected with an electrode terminal of the lead frame by wire bonding. The lead frame, the semiconductor chip and wires are sealed by a mold resin (sealing resin) by transfer molding. The die pad and the electrode terminal are exposed on the undersurface of the package.
In the semiconductor package having the foregoing structure, when a temperature cycle of heat generation and cooling is repeated due to a temperature change of an external environment and a temperature change of a semiconductor chip itself, the die bond resin may be detached from the die pad or the semiconductor chip, thus leading to detachment of the die pad and the semiconductor chip. Further, detachment of the die pad and the semiconductor chip may cause occurrence of cracking in the mold resin. When detachment and cracking occur, reliability and a life of the semiconductor package are reduced.
The foregoing detachment and cracking occur due to a difference in linear expansion coefficient among the semiconductor chip, the lead frame, the die bond resin and the mold resin. For example, when the semiconductor chip is formed of silicon and the lead frame is formed of copper, the linear expansion coefficient of the lead frame is larger than the linear expansion coefficient of the semiconductor chip. In this case, the semiconductor package has a flat shape at a normal temperature, but a projected warpage occurs due to thermal stress at a low temperature. Further, a recessed warpage occurs due to thermal stress at a high temperature. With these warpages, the foregoing detachment and cracking occur.
When detachment and cracking reach the outside of the package, it might bring about deterioration in moisture resistance and insulation, leading to reduction in reliability and life of the semiconductor package. Further, when detachment and cracking occur below the semiconductor chip, it might cause deterioration in heat dissipation and degradation in electric connection, leading to reduction in reliability and life of the semiconductor chip.
For example, in Japanese Patent Application Laid-Open No. 6-85132 (1994), a projection/recess shape is formed on the interface between a die pad and a mold resin (resin sealing member), thereby to suppress detachment of the mold resin from the die pad.
As described above, there has been a problem where detachment and cracking that occur inside the semiconductor package cause occurrence of reduction in reliability and life of the semiconductor package. Further, the foregoing technique described in Japanese Patent Application Laid-Open No. 6-85132 (1994) is one for suppressing detachment of the die pad and the mold resin, and not one capable of suppressing detachment of the die pad and the semiconductor chip.